The present invention relates generally to the cooling of electric motors. More particularly, the invention concerns a system employing a thermoelectric cooling device to cool electric motors.
Designers of devices utilizing electric motors typically desire the lowest cost motor that will meet the requirements of the particular application. Balanced against the desire to utilize the motor having the lowest cost is the need to utilize a motor that maintains a safe operating temperature. Although larger motors, having a larger wire size or longer armature stacks, are less susceptible to overheating than smaller motors, larger motors are typically more expensive to purchase and operate.
In addition, the need to maintain a safe operating temperature is amplified when speed controllers are use in conjunction with electric motors. The use of speed controllers with electric motors can cause inefficiency and a disproportionate rise in motor operating temperature when the motor speed is adjusted.
In an effort to utilize smaller and less expensive electric motors, designers have attempted to cool the smaller motors during operation to prevent overheating. However, the prior art attempts in achieving this cooling have met with only limited success.
One conventional prior art solution to the electric motor overheating problem utilizes induced ambient air flow, wherein air is induced to flow over and/or within the motor shell. Small cooling fans attached directly to the motor shaft have been used to provide such induced air flow. Another conventional prior art solution utilizes cooling fins which are added to the motor shell to increase heat transfer to the induced ambient air. The use of induced ambient air flow to cool electric motors presents a number of drawbacks and disadvantages.
One of the problems experienced in using induced ambient air flow as a cooling mechanism relates to the fact that many electric motors are used in dirty or wet environments. For example, electric motors are used to provide power to roof ventilators. Where power roof ventilators are used for commercial kitchen applications, the environment is particularly poor for the motor due to the hot, grease-entrained kitchen air exhausted by the ventilator. In these environments, it is necessary to enclose the motor to protect the internal components of the motor from the external environment by means of a separate housing. Enclosing the motor in a housing, however, restricts the cooling achievable through induced ambient air flow. Therefore, even in the housing, prior art devices have found it necessary to circulate a stream of cooling air across or within the motor shell in order to maintain a safe working temperature for the motor. This cooling air is typically drawn through an inlet conduit from outside the housing to inside the housing. There are also provided outlet holes in the housing through which an air circulation pattern is induced. For power roof ventilators, the use of this induced ambient air compromises the cleanliness of the motor by recirculating air which is near the exhaust environment of the fan. The hot, grease-entrained air that is exhausted from the kitchen can surround the motor shell and sometimes is pulled into the motor interior, causing further inefficiencies or destruction of the motor. Cooling efforts may be further limited by a layer of congealed grease surrounding the motor.
It is an object of the present invention to provide a system that provides more effective cooling of electric motors than induced air flow technologies. It is another object of the invention to provide an electric motor cooling system that does not rely on induced ambient air flow for its cooling mechanism. It is yet another object of the invention to provide an electric motor cooling system that provides sufficient cooling to a completely enclosed motor so as to prevent overheating of the motor. It is still a further object of the invention to provide an electric motor cooling system that provides sufficient cooling such that a speed controlled motor can be used in an application without overheating.
In accordance with these and other objects evident from the following description of the preferred embodiments, the present invention concerns an apparatus for cooling the internal components of an electric motor. The apparatus comprises an enclosure for protecting the internal components from an external environment and a thermoelectric cooling device adapted to cool the interior of the enclosure.
The invention also concerns a method of cooling the internal components of an electric motor having an enclosure which defines an enclosure interior and protects the internal components from an external environment. The method includes the step of delivering an electric current to a thermoelectric cooling device which is disposed between the motor interior and the external environment thereby transferring heat from the motor interior to the external environment.